1. Technical Field
The present disclosure relates to a built-in antenna device for an electronic communication device used in a multi-band communication system.
2. Description of the Related Art
Recently, rapid technical development in the Information Technology (IT) and wireless communication fields has resulted in the widespread manufacture and use of portable terminals. There have been a variety of electronic devices for communication, which provide several services to users through wireless data communication, in response to the rapid technical development. A portable terminal or mobile terminal is a general term used for any of a variety of handheld wireless communication devices, such as cell phones, smart phones, tablet PCs, notebook computers, global positioning system (GPS) devices, and personal digital assistants (PDAs). A portable terminal can be designed for use in two or more frequency bands, such as those of GSM850, GSM900, DCS 1800, PCS1900, and WCDMA band1. (GSM, DCS and PCS are acronyms for Global System for Mobile Communication, Digital Cellular System, and Personal Communication Service.)
Until recently, portable terminal antennas were external antennas, such as a helical, dipole or monopole antenna, with an omni-directional radiation characteristic. Given the problems of external antennas in terms of inconvenience and breakage, a trend has developed to equip portable terminals with built-in antennas within portable terminals. A built-in antenna typically has a flat panel structure, such as a micro strip patch antenna device or a Planar Inverted F Antenna (PIFA) device.
A typical structure of a built-in antenna includes a carrier which is formed with insulators such as polycarbonate, etc. installed in the portable terminal, and an antenna radiator of a circuit pattern shape capable of performing wireless transmission and reception in a specific frequency band mounted on this carrier.
A conventional method of manufacturing an antenna radiator used in a built-in antenna device may be one of an SUS fusion method of punching a desired pattern with a metal piece and fusing the pattern by heat on a body; an etching method of plating the whole molding body, leaving only a pattern, and removing the remainder; a double injection method of plating only a pattern on a molded body; a Laser Direct Structuring (LDS) method of engraving a conductor circuit on a 3 Dimensional (3D) surface of a component using laser and plating the component or a Printing Direct Structuring (PDS) method of directly printing a molded body with a conductive ink and plating the body.
The above-described antenna radiator used in the conventional built-in antenna device may differ slightly according to a manufacturing method of forming a pattern on a surface of a molding object and etching the surface. Because the antenna radiator is formed through a plurality of steps, production processes are complicated, productivity is reduced, and the cost of production is increased. In addition, because a dedicated space for installing the built-in antenna in the portable terminal is allocated, the size of the portable terminal is increased in order to accommodate built-in antenna.
To overcome the above-described problems, a wire type antenna formed by a polygon such as a circle, a quadrilateral, etc. may be built in. In general, there exist built-in antennas capable of simplifying production processes, improving productivity, and reducing the cost of production by forming a fixing protrusion on a case of a portable terminal, fixing a wire antenna radiator having a certain length and pattern, and electrically connecting the wire antenna radiator to a Printed Circuit Board (PCB) of the portable terminal. Also, built-in antennas capable of reducing a size of the portable terminal by reducing an installation space of the antenna radiator are in use.
Antenna mounting space is further minimized and a size of a portable terminal is reduced by designing the built-in antenna device to operate in two or more frequency bands (multi-band). Functions of the built-in antenna device have been on an expanding trend.
In general, a multi-band built-in antenna device may be a PIFA device in which there is one power feeding portion and one ground portion. This multi-band built-in antenna device was designed to cover key frequency bands of GSM850, GSM900, DCS 1800, PCS 1900, and WCDMA band1. The multi-band built-in antenna device has been widely used and may cover all of the low-frequency bands of GSM 850 to GSM900 through switching technologies in which a separate ground pad is added. Electronics for such switching adds complexity to the portable terminal.
Further, the multi-band built-in antenna device having this composition is installed or formed as one antenna radiator on a board or a carrier having a certain height installed on the board. A frequency band of GSM900 and frequency bands of DCS 1800, PCS 1900, WCDMA band1, etc. which are relatively high frequency bands generate mutual interference and cause radiation performance degradation of the multi-band built-in antenna device. Although radiation patterns of an antenna radiator having one frequency band and relatively high frequency bands are integrated with each other, they must be arranged spaced apart from each other at a certain distance. Therefore, a problem arises in that a mounting space of the multi-band built-in antenna device must be expanded.